Removal of silica from nonmetallic ores by froth flotation



I l atente d Feb. 29, 1944 v REMOVAL OF SILICA FROM NONMETALLIC ORES BY FBOTH FLOTATION Ernest J. Manet and Clinton A. liollingsworth,

Brewster, Fla., assiznors to American Cyanamid Company. New York. N. Y., a corporation of Maine No Drawing. Application April 29, 1942,

Serial No. 440,986 7 4 Claims.

This invention relates to an improved method of froth flotation of silica using certain classes of cationic reagents.

The flotation of silica by means of various cationic reagents has become of considerable importance, particularly in the beneflciation of phosphate ore from the Florida Pebble Phosphate field because of the fact that it is possible to obtain improved grade.

A number of cationic flotation reagents hav been proposed, among which the condensation product of polyalkylene polyamines with fatty acids have proven to be extraordinarily useful, both by reason of their activity and the simpler and less critical flotation procedure which may be employed. The use of reagents of this type are described and claimed in the patent to Christmann, Jayne and Erickson, No.- 2,278,060 of March 31, 1942. The present invention relates to an improvement in the process of floating silica using the abovementioned class of reagents.

In the flotation of silica, particularly in phosphate ores, the problem of slime is a critical one and in many cases it is not suflicient for best results to completely deslime a flotation feed because the flotation operation itself tends to produce secondary slime from the soft coated surfaces of the phosphate particles. This has led to a process in which the deslimed feed is subjected to polishing followed by a secondary slime as described and claimed in the patent to Mead and I Maust, No. 2,216,040 of- Scptember 24. 1940. Im-

proved results are thereby obtained, but at the expense of further processing steps. It has been found that polishing may be eliminated or reduced if the flotation is carried out very rapidly before any time has elapsed in the flotation cell which would permit the formation of secondary slime. This procedure is described and claimed in the ccpending patent of Mead and Maust, No. 2,293,470, issued August 18, 1942. High speed in flotation is therefore of great utility in the removal of silica.

The presentinvention is based on a temporary heated to approximately 100 C. or the boiling point, they become clear. The silky appearance disappears entirely and the solution remains clear for a considerable period of time even after cooling down to room temperature. In fact, it takes about 30 minutes or more before the silky appearance again sets in and clarification by heating can be repeated indefinitely. It is not known just what takes place when the colloidal material goes into solution. It may be pure solution phenomenum, or there may be some reversible chemical changes. The invention is not intended to be limited to any theory of what happens when the heating takes place. The importance of the invention, however, lies in the fact that when froth flotation is effected with the clarified solution an enormously increased flocculation speed results, and not only is it possible to obtain good grade with a very rapid flotation but even if the ordinary flotation time is used, an improvement in grade is noted. Maximum improvement results when the heating is carried out to about 100 C. but improvement starts when the heating exceeds 30 C. and is quite marked about -C. Therefore while it is preferred to heat to about C., the invention is not-broadly limited to the use of this particular temperature.

It is probable that speed of flocculation is not the only phenomena because when a small amount of reagent in water is subjected to aeration in a flotation cell, the froth characteristics are quite different. The cold reagent containing colloidal material produces a brittle froth which is brittle but will not overflow or perforate the lip of the machine. have been heated and clarified, the froth is composed of much smaller bubbles which readily overflow the lip 01' the flotation cell so that it is possible to remove a third of the water from the cell in the form of froth. Aafroth characteristics are important in most flotation operations, it

seems reasonable to assume that the improve- Fagergren flotation cell and which can be checked in larger scale operation.

A standard deslimed phosphate flotation feed of -.35 mesh obtained from phosphate deposits in the Florida Pebble P11 911 field is condi- When, however, the reagents tioned at high solids in a 2% water solution of the acetate of a condensation product of coconut oil fatty acids with a mixture of polyethylene polyamines containing predominantly dietl'iylenetriamine, triethylenetetramine and tetraethylene-pentamine. A portion was conditioned with the ordinary cold solution of the reagent and the other portions conditioned with the reagent after heating to 50, 65, 80 and 100 respectively. In each case after 10 seconds. the silica froth is skimmed as in standard test procedure, the skimming being continued for approximately 2 minutes which is normallyreferred to as a regular test. After 10 seconds,

however, a small portion of the pulp in the flotation cell is removed from the bottom and analyzed to determine the amount of beneficiation which is efiected in it for the period of 10 seconds. This is a common test used to determine speed of flocculation.

As the greatest importance of the present invention is in improved grade, the result of the tests are shown in percent of insoluble in the phosphate tailing which is directly relatable to The results of the laboratory test can be obtained on a larger scale but it is not as readily possible to determine flocculation in 10 seconds on alarge machine.

The effect of the falling temperature after clarification was tested by conditioning the same feed as in Table I with samples of the solution heated to 100 C. and then cooled down, samples being used at various temperatures on the way down. The result isshown in the following table:

Table II Per cent insoluble in Solution temperature phosphate Seconds floated Regular test. 10 seconds.

It will be apparent that the grade on the new I lar test remained substantially constant within experimental error, it being impossible to get quantative results when the percentage of insolubleisdownaslowas 1%. I

After the solution of reagent had cooled down to room temperature, a portion was allowed to stand for 30 minutes and began to take on a slightly milky appearance. When used in this state for conditioning the phosphate feed, the results were as follows:

Table III Per cent insoluble in Seconds floated phosphate 1. 60 Regular test. 4. 40 10 seconds.

scribed above and the test procedure was as follows:

Batches of feed were agitated in a laboratory Fagergren machine for 3 seconds, then silica was floated for various periods of time, after which a small amount of phosphate was discharged from the bottom of the cell while the machine was still running. This sample of phosphate was used to determine the B. P. L. and insoluble.

The metallurgical results are shown in the following table:

Table IV We at o 0 Seconds zg fga 63 d make up, then Solution made silica floated make up, then 53 gf E23 3 3 2 before taking used while hot Several hours sample of U 1d cold phosphate B. P. L. Insol. B. P. L. Insol. B. P. L. Insol.

1 Regular test. 78. 95 l. 70 78. 73 2. 30 78. 66 2. 55 5 76.10 6.05 ..l 78. 51 2. 62. 42 22. 7-1. 60 7. "8. $2 1. 95 1 l i...

The results at 10 econds with cold reagent when compared with reagent that has never been heated up is not particularly significant. When a reagent does not flocculate rapidly in an extremely short test, very wide fluctuations are to be expected. The significant factor is that the cold material in 10 seconds will give no useful grade.

When a slightly different polyalkylene polyamine condensation product was used, namely the condensation product of palm oil with a mixed polyethylene polyamine, the improvements noted were similar to reagents showing slightly different activities.

The invention has been described in more detail in conjunction with the flotation of silica from phosphate rock as this is the most important commercial process at the present time. However, the action of the reagent is primarily on the silica and the presence of the phosphate except insofar as it tends toward slime formation is secondary. Comparable improved results are obtained in floating silica away from other nonmetaliic ores.

Throughout the specification and claims the term higher fatty acids is used in its customary twelve or more carbon atoms.

We claim: 1. A method of floating silica, from a non-metallic ore which comprises conditioning an ore pulp with a solution of a condensation product of higher fatty acids with polyalkylene polyamines, at temperatures below those at which substantial taliic ore which comprises conditioning an ore quantities of imidazolines are formed by ring closure, which has beenheated until clarified and subjecting the conditioned pulp to froth flotation I before the clarified reagent has stood in the pulp for a suflicient time to reprecipitate colloidal matter.

2. A method of floating silica from a phosphate 4 ore which comprises conditioning an ore pulp with a solution of a condensation product of higher fatty acids with polyalkylene polyamines,

pulp with a solution of a condensation product of higher fatty acids with a mixture of polyethylene polyamines, at temperatures below those at which substantial quantities of imidazou'nes are formed by ring closure, which has been heated until clarified and subjecting the conditioned pulp to froth flotation before the clarified reagent has stood in the pulp for a suflicient time to reprecipitate colloidal matter.

4. A method of floating silica from a phosphate ore which comprises conditioning an ore pulp with a solution of a condensation product of higher fatty acids with a mixture of polyethylene polyamines, at temperatures below those at which substantial quantities of imidazolines are formed by ring closure, which has been heated until clarified and subjecting the conditioned pulp to froth flotation before the clarified reagent has stood in the pulp for a suflicient time to reprecipitate colloidal matter.

ERNEST J. MAUST. CLINTON A. HOLLINGSWORTH. 

